From Mark Dowson
Logician George Boolos may have solved the “hardest logic puzzle” in 1996 (22/29 December 2012, p 50). However, a handful of students of experimental psychology at the University of Sussex, UK, cracked something similar one afternoon in 1968, aided by a few beers.
Our problem was to distinguish the door that led to freedom from the door that led to death when faced by three guardians: a truth teller, a compulsive liar and a randomiser, whose words for “yes” and “no” were “ping” and “pong” (or vice versa). We didn’t need to appeal to the law of the excluded middle, and it didn’t occur to us to publish.
Leesburg, Virginia, US
